Introduction
Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) is a complex, multisystem and often debilitating disorder of unknown etiology. (1) It is a complicated disease characterized by at least six months (in paediatrics 3 months) of extreme fatigue that is not alleviated by rest and a group of other symptoms that are constant for a period of time. (1)
Post-exertional malaise (PEM) and delayed recovery are core symptoms and the most useful when making a diagnosis. (3) PEM involves a constellation of substantially disabling signs and symptoms that occur in response to physical, mental, emotional, and spiritual over-exertion. (2) In many people with chronic fatigue syndrome, the disorder begins suddenly, often after a flu-like infection or after an episode of physical or mental trauma. The diagnosis of CFS/ME relies on the typical clinical presentation and the exclusion of other causes of fatigue. A diagnosis can be made by taking a thorough history, examining the patient and using blood tests to screen for other causes of fatigue. (3) Up until now there was no test to confirm the diagnosis of CFS/ME. The two-day cardiopulmonary exercise testing (CPET) is becoming a new diagnostic method that can be used in case of suspicion of CFS/ME in attempt to evaluate presence of PEM. (5) This test, used in centres for patients with CFS/ME, has not yet published any data in paediatrics to support its use. CPET, on the other hand, provides a wealth of data on the dynamic function and coordination of the heart, lungs and muscles, as well as on the efficiency of gas exchange between mitochondria and the surrounding air, even in patients complaining about PEM.